Basics · also called STR, sell-through
Sell-through rate
Sell-through rate is the percentage of a publisher's available inventory that has been sold, usually through direct or guaranteed deals, over a given period.
Sell-through rate measures how much of the shelf got sold. A publisher forecasts how many impressions it expects in a month, and sell-through is the share committed to paying campaigns, especially direct-sold advertising and programmatic guaranteed deals.
It is a planning and sales metric. High sell-through (say, 85% in December) tells a sales team it can raise rates; low sell-through in January means more inventory flows to PMPs and the open auction as remnant inventory. TV and CTV sellers track sell-through closely around the upfronts.
Do not confuse it with fill rate. Fill rate measures, request by request, whether any ad at all was shown; sell-through measures how much inventory was sold at premium, usually in advance. A site can have 99% fill rate (because programmatic fills almost everything) and only 40% direct sell-through.
Think of it like this
Sell-through is like a theatre measuring how many seats were sold in advance at full price, before any last-minute discount tickets go on sale.
An example
A streaming service forecasts 500 million ad impressions for Q4 and sells 400 million through upfront and guaranteed deals: sell-through = 80%.
Related terms
Fill rate
Fill rate is the percentage of ad requests that are actually filled with an ad, calculated as impressions served divided by ad requests, multiplied by 100.
Direct-sold advertising
Direct-sold advertising is ad space sold by a publisher straight to an advertiser or agency through a negotiated deal, usually with a fixed price and guaranteed volume.
Ad inventory
Ad inventory is the total amount of advertising space a publisher has available to sell, usually counted in impressions across its ad slots, pages, apps or screens.
Remnant inventory
Remnant inventory is ad space a publisher has not sold through direct deals, which is then offered through programmatic channels, networks or house ads, usually at lower prices.
Upfronts
Upfronts are annual events and negotiations, mainly in the US, where TV networks and streaming services present upcoming programming and advertisers commit budgets in advance for the coming season.